1. Field of the Invention
The present invention relates to a process for preparing optically active 1-substituted-3-hydroxy-1-butene or its ester derivatives, and, more particularly, to a process for preparing optically active 1-substituted-3-hydroxy-1-butene or its ester derivatives which comprises treating racemic 1-substituted-3-hydroxy-1-butene or its ester derivatives with a lipase.
The products of the present invention can be used, for example, as a raw material of azetidinone compounds disclosed in Japanese Patent Application Laid-open No. 207373/1986. The inexpensive and simple preparation of the compounds is expected to make great contributions to the development in this field.
2. Description of the Background Art
The demand for optically active compounds are increasing in recent years in such areas as pharmaceuticals, agrichemicals, cosmetics, liquid crystals, and the like. Because synthesis of optically active compounds have been handicapped in terms of the production cost and the technology, the research in this area have remained only at a preliminary stage. The recent increase in their demands, however, has advanced the technology for their synthesis, offering more opportunities for their use.
A conventional process for producing optically active compounds involves selective reduction of carbonyl compounds. High prices of reducing agents and the requirements of special procedures in their handling have been problems in such a conventional process. A process in which microorganisms or enzymes produced therefrom are used, on the other hand, have had still to be improved in the selectivity, the reaction substrate concentration, and the like in order to apply them to a commercial production.
According to the process of the present invention in which an alcohol compound protected by an acyl group is used as a substrate can produce a desired optically active alcohol or its acyl-protected derivative in a high yield and in high optical purity under mild conditions by the treatment of the acylated alcohol substrate with a lipase. The process can provide a high substrate concentration at a small consumption of a lipase, and can be adaptable to large scale industrial production.
In view of this situation, the present inventors have undertaken extensive studies, and have found that an optically active 1-substituted-3-hydroxy-1-butene or its derivative represented by formula (II) or (III), ##STR3## could be prepared in a high yield and a high selectivity by a simple process in which an ester derivative of racemic 1-substituted-3-hydroxy-1-butene of formula (I), ##STR4## is treated with a lipase to effect asymmetric hydrolysis.
In the above formulae (I) to (III), R.sub.1 is an alkyl group having 1-8 carbon atoms, an aryl group having 6-10 carbon atoms, an alkoxy group having 1-6 carbon atoms, or an aryloxy group having 6-10 carbon atoms, wherein hydrogen atoms on the carbon atoms of the alkyl, aryl, alkoxy, or aryloxy group may optionally be substituted by alkyl, aryl, hydroxyl, alkoxy, alkylthio, or arylthio group, and R.sub.2 is a hydrogen atom, an alkyl group having 1-8 carbon atoms, an aryl group having 6-10 carbon atoms, a halogen atom, an alkoxy group having 1-6 carbon atoms, an aryloxy group having 6-10 carbon atoms, an alkylsulfonyloxy group having 1-8 carbon atoms, an arylsulfonyloxy group having 6-10 carbon atoms, an alkylthio group having 1-8 carbon atoms, or an arylthio group having 6-10 carbon atoms, wherein hydrogen atoms on the carbon atoms of the alkylsulfonyloxy, arylsulfonyloxy, alkylthio, or the arylthio group may optionally be substituted by halogen, alkyl, aryl, hydroxyl, or alkoxy group, and in formulae (II) and (III) the secondary hydroxyl group has either R or S configuration.